An advantage of a conventional SS-OCT system over its spectral domain counterparts can be the high acquisition speed, which makes SS-OCT a promising solution to many real world clinical applications. The acquisition rate of SS-OCT can be mainly limited by the scanning speed of the swept laser source, and the sensitivity of the photodetector, while the acquisition speed of a spectral domain (“SD”) OCT system can be bottlenecked by the data acquisition speed of the line sensor, which can be confined by the speed of the circuitry.
Recently, the upper limit of the scanning speed of swept source lasers has been pushed higher and higher. Swept source lasers with about a 200 kHz scanning speed can be common in the market. However, the higher scanning speed has imposed a more demanding requirement on the sensitivity of the photodetectors, since the maximum exposure time of the photodetector can be upper-bounded by the scanning period. Because biomedical samples such as tissues can be of particular interest, which can be highly scattering, shorter exposure time can potentially reduce the signal-to-noise ratio (“SNR”) at the detector. Therefore, a highly sensitive sensor can be desired when using a SS-OCT system.
High performance photodetectors in the near infrared (“NIR”) range are uncommon. For example, a typical value of an InGaAs avalanche photodetector at about 1300 nm can be around 1.5˜2.5 A/W. Conversely, there are plenty of options for photodetectors in the visible range. Silicon avalanche photodetectors can usually achieve a sensitivity as high as about 25 A/W. Other solutions, such as charge-coupled device (“CCD”), may also be available in visible spectrum.
Thus, it may be beneficial to provide an exemplary high-sensitive swept-source optical coherence tomography system and method, which can overcome at least some of the deficiencies described herein above.